EXG1 encodes the major secreted and soluble-cell-wall glucan 1,3-beta-glucosidase of Saccharomyces cerevisiae. The mature glycoprotein is processed for secretion, localizes to the extracellular region and fungal-type cell wall, hydrolyzes beta-1,3-glucans from their nonreducing ends with additional beta-1,6-linked substrate activity in vitro, and participates in fungal-type cell-wall beta-glucan metabolism.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000272 polysaccharide catabolic process | IEA GO_REF:0000002 | MODIFY | Summary: InterPro maps the GH5 domain to the broad parent process of polysaccharide catabolism. Reason: The GH5 match is real and Exg1 hydrolyzes beta-glucans, but the generic polysaccharide-catabolism parent should be redirected to the fungal-type cell-wall beta-glucan remodeling process that captures Exg1's in vivo role without asserting net bulk glucan catabolism. Proposed replacements: fungal-type cell wall beta-glucan metabolic process Supporting Evidence: PMID:11471729 the enzyme has a broad specificity for beta-1,3-linkages as well as beta-1,6-linkages, and also for other beta-glucosidic linked substrates, such as cellobiose and pNPG |
| GO:0000324 fungal-type vacuole | HDA PMID:26928762 One library to make them all: streamlining the creation of y... | MARK AS OVER ANNOTATED | Summary: The SWAT N-terminal GFP screen reported a vacuole localization for EXG1. Reason: The SWAT acceptor screen drove N-terminal GFP fusions from the constitutive SpNOP1 promoter in vegetative cells; for signal-peptide proteins such as Exg1 it placed a generic Kar2 signal peptide plus GFP immediately upstream of the mature cargo. Mature Exg1 normally has a cleaved signal peptide and propeptide, and direct evidence places it in secreted medium and the soluble cell-wall fraction. This ectopic, N-terminally tagged vacuole call is therefore unlikely to represent a native site of Exg1 action. Supporting Evidence: PMID:26928762 To demonstrate the SWAT approach we constructed an acceptor library using an acceptor module that included the constitutive SpNOP1 promoter 19 and a GFP tag (SWAT-GFP). PMID:19129178 Identity was determined by mass spectrometry and included Hsp150, Cts1, Scw4, Scw10, Exg1, Cis3, and Ygp1, proteins known to be secreted by S. cerevisiae |
| GO:0004338 glucan exo-1,3-beta-glucosidase activity | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT places glucan exo-1,3-beta-glucosidase activity at the Saccharomycetes EXG1/XOG1/SPR1 subclade. Reason: PTN001262687 is a Saccharomycetes node seeded by Candida XOG1 and multiple experimentally annotated budding-yeast glucanases, including EXG1 itself; the node assignment is consistent with direct recombinant Exg1 enzyme assays. Propagation Review Root cause: NO FAILURE CORE Sources checked: PANTHER:PTN001262687 · Saccharomycetes EXG1/XOG1 glucanase node SUPPORTS TRANSFER The node carries the exact exo-1,3-beta-glucosidase activity in the clade containing S. cerevisiae EXG1. Supporting Evidence: file:interpro/panther/PTHR31297/PTHR31297-paint.tsv PTHR31297 PTN001262687 GO:0004338 F IBD false PMID:11471729 Yeast exo-beta-1,3-glucanase gene (EXG1) was expressed in Escherichia coli and the recombinant enzyme (Exg1p) was characterized. |
| GO:0004338 glucan exo-1,3-beta-glucosidase activity | IDA PMID:11471729 Characterization of recombinant yeast exo-beta-1,3-glucanase... | ACCEPT | Summary: Recombinant S. cerevisiae Exg1 has exo-beta-1,3-glucanase activity. Reason: Suzuki and colleagues expressed EXG1 in E. coli and biochemically characterized the recombinant enzyme, confirming beta-1,3-linked glucan hydrolase activity. Supporting Evidence: PMID:11471729 Yeast exo-beta-1,3-glucanase gene (EXG1) was expressed in Escherichia coli and the recombinant enzyme (Exg1p) was characterized. PMID:41439696 Exo-β-1,3-glucanase EXG1 (ScEXG1) from Saccharomyces cerevisiae hydrolyzes β-1,3-glucans and exhibits transglycosylation activity |
| GO:0004338 glucan exo-1,3-beta-glucosidase activity | IEA GO_REF:0000120 | ACCEPT | Summary: The EC/Rhea electronic mapping gives the same exact exo-1,3-beta-glucanase activity established for Exg1. Reason: EC:3.2.1.58 is the correct enzyme class for mature Exg1, and direct recombinant-enzyme assays support retaining this exact activity. Supporting Evidence: PMID:11471729 Yeast exo-beta-1,3-glucanase gene (EXG1) was expressed in Escherichia coli and the recombinant enzyme (Exg1p) was characterized. |
| GO:0004338 glucan exo-1,3-beta-glucosidase activity | ISS GO_REF:0000024 | ACCEPT | Summary: UniProt transfers the exact exo-1,3-beta-glucanase activity from Candida albicans Xog1. Reason: Candida Xog1 and S. cerevisiae Exg1 are in the same PTHR31297:SF1 subfamily and in the PAINT node that carries glucan exo-1,3-beta-glucosidase activity, so the curator-reviewed similarity transfer agrees with the target's direct biochemical evidence. Propagation Review Root cause: NO FAILURE CORE Sources checked: UniProtKB:P29717 · Candida albicans XOG1 SUPPORTS TRANSFER Xog1 is a same-subfamily fungal exo-1,3-beta-glucanase. Supporting Evidence: file:interpro/panther/PTHR31297/PTHR31297-paint.tsv PTHR31297 PTN001262687 GO:0004338 F IBD false |
| GO:0004338 glucan exo-1,3-beta-glucosidase activity | ISS PMID:9748433 New potential cell wall glucanases of Saccharomyces cerevisi... | ACCEPT | Summary: SGD transfers exo-1,3-beta-glucosidase activity from the Bgl2-like cell-wall protein Scw4. Reason: The transferred GO term is core for Exg1, but not because Scw4 supports it: the 1998 source paper identified Scw4 as Bgl2-like and could not demonstrate exo- or endoglucanase activity for purified Scw4. This ISS row is redundant with direct recombinant Exg1 assays and has a source-side propagation defect. Propagation Review Root cause: SOURCE BAD Failure modes: WRONG ORTHOLOG OR PARALOG SOURCE EVIDENCE WEAK Sources checked: SGD:S000003514 · S. cerevisiae Scw4 SOURCE BAD Scw4 is Bgl2-like rather than a PTHR31297 member, and the source paper did not demonstrate exo- or endoglucanase activity for Scw4. Supporting Evidence: PMID:9748433 attempts to demonstrate exo- or endoglucanase activity of Scw4p failed, suggesting that this protein might preferentially catalyze a transglucosylation reaction. |
| GO:0004553 hydrolase activity, hydrolyzing O-glycosyl compounds | IEA GO_REF:0000002 | MODIFY | Summary: The InterPro2GO hydrolase parent is a true but too-general ancestor of Exg1's exact activity. Reason: Exg1 is a glycoside hydrolase, but the parent term only says that it hydrolyzes an O-glycosyl compound; the exact glucan exo-1,3-beta-glucosidase term is supported by both PAINT and direct enzyme assays. Proposed replacements: glucan exo-1,3-beta-glucosidase activity Supporting Evidence: PMID:11471729 Yeast exo-beta-1,3-glucanase gene (EXG1) was expressed in Escherichia coli and the recombinant enzyme (Exg1p) was characterized. |
| GO:0005576 extracellular region | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT places extracellular activity at the fungal EXG1/XOG1 node. Reason: PTN001262686 is the fungal node that covers the secreted EXG1/XOG1 glucanases, and the transfer matches direct recovery of budding-yeast Exg1 from the cell exterior and extracellular culture medium. Propagation Review Root cause: NO FAILURE CORE Sources checked: PANTHER:PTN001262686 · fungal EXG1/XOG1 extracellular glucanase node SUPPORTS TRANSFER The node carries extracellular region in the clade containing Exg1 and other secreted fungal glucanases. Supporting Evidence: file:interpro/panther/PTHR31297/PTHR31297-paint.tsv PTHR31297 PTN001262686 GO:0005576 C IBD false PMID:9748433 three of these proteins were identified as the known proteins beta-exoglucanase 1 (Exg1p), beta-endoglucanase (Bgl2p), and chitinase (Cts1p) PMID:19129178 Identity was determined by mass spectrometry and included Hsp150, Cts1, Scw4, Scw10, Exg1, Cis3, and Ygp1, proteins known to be secreted by S. cerevisiae |
| GO:0005576 extracellular region | IDA PMID:19129178 Phospholipid transfer protein Sec14 is required for traffick... | ACCEPT | Summary: Mass spectrometry detected Exg1 among proteins secreted into the medium. Reason: Curwin and colleagues found Exg1 in extracellular medium after a secretion assay and mass spectrometry, directly supporting the extracellular-region localization. Supporting Evidence: PMID:19129178 Identity was determined by mass spectrometry and included Hsp150, Cts1, Scw4, Scw10, Exg1, Cis3, and Ygp1, proteins known to be secreted by S. cerevisiae |
| GO:0005576 extracellular region | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt subcellular-location mapping records Exg1 as secreted. Reason: Exg1 has a signal peptide, is processed for secretion, and was recovered from both intact-cell wall extracts and secreted medium, so the conservative UniProt extracellular mapping is correct. Supporting Evidence: file:genes/yeast/EXG1/EXG1-uniprot.txt CC -!- SUBCELLULAR LOCATION: Secreted, cell wall {ECO:0000269|PubMed:9748433}. CC Secreted {ECO:0000269|PubMed:9748433}. |
| GO:0005975 carbohydrate metabolic process | IEA GO_REF:0000002 | MODIFY | Summary: InterPro maps the GH5 signature to a generic carbohydrate metabolic process parent. Reason: The row is directionally correct because Exg1 acts on beta-glucan carbohydrates, but it is a broad parent of the more informative fungal cell-wall beta-glucan metabolism term. Proposed replacements: fungal-type cell wall beta-glucan metabolic process Supporting Evidence: PMID:11471729 the enzyme has a broad specificity for beta-1,3-linkages as well as beta-1,6-linkages, and also for other beta-glucosidic linked substrates, such as cellobiose and pNPG |
| GO:0009251 glucan catabolic process | IBA GO_REF:0000033 | MARK AS OVER ANNOTATED | Summary: A PTHR31297 family-root PAINT node transfers glucan catabolism from Aspergillus exgB/exgD-like seeds. Reason: Exg1 hydrolyzes beta-glucan substrates, so glucan catabolism is not biologically impossible, but the PTN001262628 assertion was seeded by Aspergillus SF34/SF39 members outside the EXG1/Spr1/XOG1 SF1 clade. Exg1 also prefers small disaccharide and pNPG substrates over the beta-1,3 and beta-1,6 polymers laminaran and pustulan and is strongly inhibited by high laminaran concentrations, while high laminaribiose can drive transglucosidation in vitro. The better scoped in vivo process is fungal-type cell-wall beta-glucan metabolism from PTN001262686, not bulk glucan catabolism. Propagation Review Root cause: TERM SCOPING PROBLEM Failure modes: WRONG ORTHOLOG OR PARALOG GRANULARITY MISMATCH Sources checked: PANTHER:PTN001262628 · broad Aspergillus exgB/exgD-like glucan-catabolism node SUPPORTS SOURCE BUT NOT TARGET The node is seeded by Aspergillus exgD/exgB SF34/SF39 members and is broader and less well scoped than the PTN001262686 wall beta-glucan node for S. cerevisiae EXG1. Supporting Evidence: file:interpro/panther/PTHR31297/PTHR31297-paint.tsv PTHR31297 PTN001262628 GO:0009251 P IBD false PMID:11471729 Kinetic analyses indicate that the enzyme prefers small substrates such as laminaribiose, gentiobiose, and pNPG rather than polysaccharide substrates, such as laminaran or pustulan. PMID:11471729 With a high concentration of laminaribiose, the enzyme catalyzed transglucosidation forming laminarioligosaccharides. The enzyme was strongly inhibited with high concentrations of laminaran. |
| GO:0009277 fungal-type cell wall | IDA PMID:9748433 New potential cell wall glucanases of Saccharomyces cerevisi... | ACCEPT | Summary: Exg1 was N-terminally sequenced from soluble proteins released from intact yeast cell walls. Reason: Cappellaro and colleagues used nonpermeant surface biotinylation, intact cell extraction, and N-terminal sequencing to identify Exg1 as a soluble cell-wall protein. Supporting Evidence: PMID:9748433 three of these proteins were identified as the known proteins beta-exoglucanase 1 (Exg1p), beta-endoglucanase (Bgl2p), and chitinase (Cts1p) |
| GO:0009277 fungal-type cell wall | IEA GO_REF:0000117 | ACCEPT | Summary: ARBA maps Exg1 to the fungal-type cell wall. Reason: The electronic prediction matches direct N-terminal sequencing of Exg1 from soluble proteins released from intact cell walls. Supporting Evidence: PMID:9748433 three of these proteins were identified as the known proteins beta-exoglucanase 1 (Exg1p), beta-endoglucanase (Bgl2p), and chitinase (Cts1p) |
| GO:0031505 fungal-type cell wall organization | ISS PMID:9748433 New potential cell wall glucanases of Saccharomyces cerevisi... | KEEP AS NON CORE | Summary: SGD transfers fungal cell-wall organization from Bgl2-like Scw4. Reason: EXG1 is not the SCW4/SCW10 pair tested for mating efficiency in the 1998 paper, but Exg1 has direct genetic evidence for modulating cell-wall beta-glucan assembly. The Scw4-derived ISS rationale is weak, but the existing cellular-component organization term is defensible as a non-core consequence of EXG1 dosage changes in the cell wall rather than as a direct molecular activity. Propagation Review Root cause: PROPAGATION BAD Failure modes: WRONG ORTHOLOG OR PARALOG Sources checked: SGD:S000003514 · S. cerevisiae Scw4 SUPPORTS SOURCE BUT NOT TARGET SCW4/SCW10 phenotypes motivated the original ISS, but EXG1-specific cell-wall beta-glucan phenotypes are the better support for this non-core organization row. Supporting Evidence: PMID:7565587 Overexpression of EXG1 on a 2 mu plasmid led to reduction in a cell wall beta 1,6-glucan and caused killer resistance in wild type cells; while the exg1 delta mutant displayed modest increases in killer sensitivity and beta 1,6-glucan levels. |
| GO:0044042 glucan metabolic process | IMP PMID:7565587 Regulation of cell wall beta-glucan assembly: PTC1 negativel... | MODIFY | Summary: Exg1 dosage changes beta-glucan levels and killer-toxin sensitivity. Reason: The 1995 genetic data establish that Exg1 modulates fungal cell-wall beta-glucan assembly; the current row is correct but should be scoped to the more specific fungal-type cell-wall beta-glucan metabolic process that current PAINT also transfers to EXG1. Proposed replacements: fungal-type cell wall beta-glucan metabolic process Supporting Evidence: PMID:7565587 These results suggest that Ptc1p/Cwh47p and Pbs2p play opposing regulatory roles in cell wall glucan assembly, and that this is effected in part by modulating Exg1p activity. |
| GO:0046557 glucan endo-1,6-beta-glucosidase activity | IDA PMID:11471729 Characterization of recombinant yeast exo-beta-1,3-glucanase... | MODIFY | Summary: Recombinant Exg1 hydrolyzes beta-1,6-linked small substrates in vitro, but its profile fits beta-glucosidase activity rather than endo-1,6 cleavage. Reason: Suzuki and colleagues found activity toward beta-1,6-linked gentiobiose, but also found that Exg1 prefers small substrates over the beta-1,6 polymer pustulan. That exo/small-substrate profile supports the broader beta-glucosidase activity term rather than an endo-1,6-beta-glucosidase activity, and PAINT assigns the endo-1,6 term to a different Saccharomycetales/PomBase paralog node. Proposed replacements: beta-glucosidase activity Supporting Evidence: PMID:11471729 Kinetic analyses indicate that the enzyme prefers small substrates such as laminaribiose, gentiobiose, and pNPG rather than polysaccharide substrates, such as laminaran or pustulan. file:interpro/panther/PTHR31297/PTHR31297-paint.tsv PTHR31297 PTN001262669 GO:0046557 F IBD false |
| GO:0070879 fungal-type cell wall beta-glucan metabolic process | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT places fungal-type cell-wall beta-glucan metabolism at the EXG1/XOG1 fungal node. Reason: The PTN001262686 transfer matches both the conserved extracellular glucanase clade and direct yeast genetic evidence that Exg1 activity modulates cell-wall beta-glucan assembly. Propagation Review Root cause: NO FAILURE CORE Sources checked: PANTHER:PTN001262686 · fungal EXG1/XOG1 extracellular glucanase node SUPPORTS TRANSFER The fungal node carries beta-glucan metabolism for the extracellular EXG1/XOG1 clade. Supporting Evidence: file:interpro/panther/PTHR31297/PTHR31297-paint.tsv PTHR31297 PTN001262686 GO:0070879 P IBD false PMID:7565587 These results suggest that Ptc1p/Cwh47p and Pbs2p play opposing regulatory roles in cell wall glucan assembly, and that this is effected in part by modulating Exg1p activity. |
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Download this section (compressed HTML)Q: Does Exg1-mediated beta-glucan transglycosylation occur in the yeast cell wall in vivo, or is the 2026 ScEXG1 transglycosylation profile an in vitro side activity favored only at high laminaribiose and low enzyme concentrations?
Experiment: Compare beta-glucan oligosaccharide products from wild-type, exg1 null, and catalytically complemented cells by linkage-sensitive LC-MS/MS under native cell-wall remodeling conditions.
Type: glycan structural profiling
Major exo-1,3-beta-glucanase of the cell wall; involved in cell wall beta-glucan assembly; exists as three differentially glycosylated isoenzymes; EXG1 has a paralog, SPR1, that arose from the whole genome duplication
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